I also like my seams to nest. Seems (
) I get a better match that way, so unless my light fabric so light weight that the darker fabric will show thru, I press so the seams nest. Having said that, to repress half your blocks will take a bit of time. The only way I've found to make a seam go the other way after it's been pressed is to first press flat, like when you set the seam, then press the way I want it to go. You will have to be extra careful because all your blocks have bias edges and all the handling & ironing may distort them.
As suggested by a previous poster, try re ironing a couple blocks then decide if it's worth the effort.